All Publications


  • Fine-Tuning Semiconducting Polymer Self-Aggregation and Crystallinity Enables Optimal Morphology and High-Performance Printed All-Polymer Solar Cells. Journal of the American Chemical Society Wu, Y., Schneider, S., Walter, C., Chowdhury, A. H., Bahrami, B., Wu, H., Qiao, Q., Toney, M. F., Bao, Z. 2019

    Abstract

    Polymer aggregation and crystallization behavior play a crucial role in the performance of all-polymer solar cells (all-PSCs). Gaining control over polymer self-assembly via molecular design to influence bulk-heterojunction active-layer morphology, however, remains challenging. Herein, we show a simple yet effective way to modulate the self-aggregation of the commonly used naphthalene diimide (NDI)-based acceptor polymer (N2200), by systematically replacing a certain amount of alkyl side-chains with compact bulky side-chains (CBS). Specifically, we have synthesized a series of random copolymer (PNDI-CBSx) with different molar fractions (x = 0-1) of the CBS units and have found that both solution-phase aggregation and solid-state crystallinity of these acceptor polymers are progressively suppressed with increasing x as evidenced by UV-vis absorption, photoluminescence (PL) spectroscopies, thermal analysis, and grazing incidence X-ray scattering (GIWAXS) techniques. Importantly, as compared to the highly self-aggregating N2200, photovoltaic results show that blending of more amorphous acceptor polymers with donor polymer (PBDB-T) can enable all-PSCs with significantly increased PCE (up to 8.5%). The higher short-circuit current density (Jsc) results from the smaller polymer phase-separation domain sizes as evidenced by PL quenching and resonant soft X-ray scattering (R-SoXS) analyses. Additionally, we show that the lower crystallinity of the active layer is less sensitive to the film deposition methods. Thus, the transition from spin-coating to solution coating can be easily achieved with no performance losses. On the other hand, decreasing aggregation and crystallinity of the acceptor polymer too much reduces the photovoltaic performance as the donor phase-separation domain sizes increases. The highly amorphous acceptor polymers appear to induce formation of larger donor polymer crystallites. These results highlight the importance of a balanced aggregation strength between the donor and acceptor polymers to achieve high-performance all-PSCs with optimal active layer film morphology.

    View details for DOI 10.1021/jacs.9b10935

    View details for PubMedID 31793773

  • Effect of Extensional Flow on the Evaporative Assembly of a Donor-Acceptor Semiconducting Polymer ACS APPLIED ELECTRONIC MATERIALS Nikzad, S., Wu, H., Wang, G., Yan, H., Schneider, S. A., Toney, M. F., Bao, Z. 2019; 1 (11): 2445–54
  • Fullerene derivative induced morphology of bulk heterojunction blends: PIPCP:PC61BM RSC ADVANCES Huang, T., Yan, H., Abdelsamie, M., Savikhin, V., Schneider, S. A., Ran, N. A., Thuc-Quyen Nguyen, Bazan, G. C., Toney, M. F. 2019; 9 (8): 4106–12

    View details for DOI 10.1039/c8ra10488c

    View details for Web of Science ID 000459896700002